1. Field of the Invention
This invention pertains to a process for making silicon-containing compounds employing an azo free-radical initiation system.
2. Description of Related Art
There are generally three methods for adding a silane to an olefinic compound. They are the Grignard method, the precious metal catalyst route and the free-radical route. The method employed in the process of this invention is characterized by the following advantages: (1) reaction products have excellent crosslinking properties as a result of their enrichment in disilylated component; (2) reactions proceed safely, quickly, and with good yield; (3) the initiators are highly selective for the desired products; (4) no separation of initiator is necessary since formation of byproducts is minimal and the products do not harm the system; (5) substantially no undesirable color is introduced into the final products by initiator or byproduct; and (6) economical compared to the precious metal catalyst route.
Despite the known methods for adding an olefinic compound to a silane, none has employed an azo free-radical initiator with the particular olefinic substrates described in the process of this invention characterized as it is by having at least 10 percent of a disilylated component in the final hydrosilylated product. Careful selection of the olefinic compound, choice of azo free-radical initiation, and production of at least 10 percent of disilylated material in the final product achieves process advantages 1 to 6 described above. These products have special utility in a wide range of compositions that cure in the presence of atmospheric moisture; for example, sealants, caulks and the like.